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I have been learning IEEE 802.11ad and the following processing algorithm

I was wondering what is the need for spreading with Golay sequence. I am guessing it has to with something like spread spectrum in CDMA applications.

Does anyone know why and whats the purpose of using such a block after modulation block?

Thanks

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  • $\begingroup$ Is this your source: cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/… ? Mind including it in your question? $\endgroup$ – Deve May 27 '15 at 8:54
  • $\begingroup$ sure i will include reference. $\endgroup$ – Tyrone May 27 '15 at 9:43
  • $\begingroup$ @deve the reference is included. Mind me asking how were you able to find it! $\endgroup$ – Tyrone May 27 '15 at 13:25
  • $\begingroup$ I googled "IEEE 802.11ad" and this was one of the first results ;) Btw, why did you remove the hint that the block diagram is from 802.11ad? I think this is helpful for answering the question. $\endgroup$ – Deve May 27 '15 at 13:32
  • $\begingroup$ Ok I thought it was irreleavant. I will add again. $\endgroup$ – Tyrone May 27 '15 at 13:34
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It is just the control channel that is spread. It appears that it is spread primarily to make the signal more robust in the face of frequency selective fading, which is probably a major problem at 60 GHz. It is easy to use spreading to get the robustness because the data rate of the control channel is low. In other words, the spreading is fulfilling two roles: converting the low control channel data rate to the high OFDM symbol rate, and increasing the control channel's robustness.

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  • $\begingroup$ Thanks, so when we spread the spectrum of information signal, do we increase the data rate? I thought with spreading the rates decrease and thus more reliable. The reason I am asking is because you mentioned that we are coverting a low data rate to high OFDM data rate. Are usually higer rates achieved with spreading the spectrum? $\endgroup$ – Tyrone May 27 '15 at 14:03
  • $\begingroup$ Sorry, poor use of terminology. Spreading increases the symbol (or chip) rate, not the data rate. Will edit the answer. $\endgroup$ – Jim Clay May 27 '15 at 14:12
  • $\begingroup$ thanks, which makes me think, does it increase of decrease the data rates? $\endgroup$ – Tyrone May 27 '15 at 14:34
  • $\begingroup$ Spreading doesn't change the data rate at all. $\endgroup$ – Jim Clay May 28 '15 at 1:10
  • $\begingroup$ but in your answer you mentioned that we convert the low control channel data rate to high OFDM symbol rate, I dont understnad what you meant by this...i.e. how did we end up with OFDM $\endgroup$ – Tyrone May 28 '15 at 1:59

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